The Science & Technology
Cambridge - Monday 4th to
Wednesday 6th September 2017
article posted 17 Apr 2017
Adja Touré graduated from the Chemistry, Physics and Electronics Engineering School of Lyon (France), specialising in chemistry and engineering process and from the University of Lyon where she undertook a masters degree in Engineering for Health and Medicine. She then started a PhD, working with Dr Jamieson K. Christie at Loughborough University, studying computer simulations of biomaterials for medical applications. Adja's research involves studying the influence of fluorine addition on the bioactivity of phosphate bioactive glasses.
Molecular dynamics simulation of phosphate based
bioactive glasses containing fluorine
A.B.R. Touré*, E. Mele, J.K. Christie
Department of Materials, Loughborough University,
Loughborough, LE11 3TU, UK
Phosphate-based bioactive glasses (PBGs) are used as biomaterials in many biomedical
fields such as orthopaedics and dental surgery [1,2]. In addition to their bone cell growth
and antigen expression enhancement properties , PBGs completely dissolve in an
aqueous environment and the dissolution behaviour can be controlled by the glass
composition and chemistry. In the biomedical field, this is an interesting property
for drug or therapeutic metal ion release applications.
In this work, we aim at precisely describing the effect of integrating fluorine into the
structure of PBGs. Since structural properties and bioactive behaviour are closely related,
we will henceforth better understand the bioactivity of phosphate based glasses.
This project focuses on the molecular dynamics simulation of the fluorinated phosphate-based
bioactive glass (F- PBG) systems
In a previous study , the structural changes associated with the addition of fluorine
in the systems
were studied using ab initio molecular dynamics.
The first effect observed was the oxygen replacement, in the
tetrahedron, by a
fluorine atom leading to a local decrease of network connectivity which is likely to
increase the bioactivity. The possible presence of clusters of modifier-rich and network-rich
regions which are likely to decrease bioactivity was considered insignificant due to the
large amount of P-F bonding. The study concluded that the bioactivity was not
substantially altered following the addition of fluorine.
We use classical molecular dynamics [5,6] to atomically model the structure of those
fluorinated phosphate BGs on a larger length scale. To do so, we developed an empirical
force field with ionic charges and the use of a shell model  for polarisation effects.
The empirical fitting was performed by reproducing the structure of relevant bulk crystals:
with the Buckingham potential. The molecular dynamics simulations are performed on
the following systems
) (50-x/2 ) - (CaO) (50-x/2) - (CaF2
with x = 0, 5,10 and using the molecular
dynamics code DL_POLY Classic. The amount of CaF2
is increased while the network
connectivity is kept constant. Since the network connectivity of the glass is the main
structural parameter affecting the bioactivity of the BGs, we are aim at simulating
F-PBGs exhibiting similar bioactivities. In this talk, we present a full analysis of
the structure of F-PBG, including the extent of any fluorine clustering.
1. Abou Neel, E., Pickup, D. M., Valappil, S. P., Newport, R. J., and Knowles, J. C. (2009). Journal of Materials Chemistry, 19(6):690-701.
2. Salih, V., Franks, K., James, M., Hastings, G. W., Knowles, J. C., and Olsen, I. (2000). Journal of Materials Science: Materials in Medicine, 11(10):615-620.
3. Hoppe, A., Guldal, N. S., and Boccaccini, A. R. (2011). Biomaterials, 32(11):2757-2774
4. Christie, J.K., Ainsworth, R.I. & de Leeuw, N.H., 2014. Ab initio molecular dynamics simulations of structural changes associated with the incorporation of fluorine in bioactive phosphate glasses. Biomaterials, 35(24):6164-6171.
5. Allen, M. P. and D.J, (1987). Computer Simulation of Liquids. Clarendon Press
6. Frenkel, D. and Smit, B. (2002). Understanding Molecular Simulation: From Algorithms to Applications. Academic Press.
7. Dick, B. G. and Overhauser, A. W. (1958). Physical Review, 112(1):90-103.